04
Oct

AN INVESTIGATION ON THE SUITABILE CONSTITUTIVE LAW FOR MODELLING JAKARTA RED CLAY

Written by Gouw Tjie Liong, Ir., M.Eng, ChFC, PhD. Posted in Geotechnic, Technical Paper & Presentation (Others)

Abstract:Having the origin from the sedimentation of volcanic materials, many experienced Indonesian geotechnical engineers have long suspected that Jakarta reddish and grayish clay may have different characteristics compared to other clayey soils known in many geotechnical text books. Despite of carefully derived design parameters, experiences in the execution of deep excavation, be it open cut slope or protected excavation by either contiguous bored pile or diaphragm walls, often show that the performance of the geotechnical structures were better than predicted by the available design geotechnical software. Although, some engineers have started using more advanced constitutive soil models, such as: Hyperbolic and Cam Clay models. Undoubtedly, many engineers still use the bilinear Mohr-Coulomb model in their analysis. So far, to the author knowledge, there is no published paper discussing about the suitability of the soil models for modelling Jakarta red clay, in particular. Therefore, the author tried to find out which soil constitutive models can better predict the behavior of the Jakarta reddish/grayish clay. Available models in PLAXIS software, e.g.; Mohr-Coulomb, Hardening (hyperbolic), and Soft Soil models, were tried by simulating isotropically consolidated undrained triaxial test and compared it with the actual test data. At this stage it was found that none of the model can correctly predict the stress strain curve neither the correct stress path.

Keywords: Volcanic Origin Clay, Jakarta Clay, Mohr Coulomb Model, Hardening Soil Model, Soft Soil Model, Plaxis

Download full paper: GTL-141021-FindingSuitableModel

04
Oct

PERLUKAH GIANT SEA WALL UNTUK JAKARTA?

Written by Gouw Tjie Liong, Ir., M.Eng, ChFC, PhD. Posted in Geotechnic, Note and Discussion

1.       MACET, BANJIR dan Kekurangan air bersih

Walaupun penuh dengan permasalahan, Jakarta merupakan kota yang ‘dicintai’ jutaan penduduknya.  Dua masalah utama adalah kemacetan lalu lintas dan kemacetan air alias banjir. Pagi hari begitu keluar pintu, kita sudah dihadapkan dengan kemacetan, siang hari pergi rapat bersitegang melawan padatnya lalu-lintas, sore hari saat pulang kantor kembali lagi harus berjuang melawan kemacetan. tidak jarang kita menghabiskan waktu 3 – 6 jam di jalan jalan kota Jakarta, membakar bahan bakar bersubsidi ataupun tidak. Ribuan bahkan mungkin puluhan ribu liter bensin terbakar percuma dan mengotori udara Jakarta. Ketika hujan datang, segera saja genangan dimana-mana, menambah macetnya Jakarta. Januari dan Februari pemandangan banjir menjadi biasa!! Dahulu banjir lima tahunan,  kini pada tahun 2014, bukan lagi lima tahun sekali, tetapi menjadi sebulan lima kali banjir! Luar biasa!! Bahkan yang katanya musim kemarau, Juli dan Agustus 2014 ini beberapa wilayah juga tergenangi banjir, walapun hanya hujan selama satu dua jam saja!!! Ironisnya, kota yang punya “banyak air” ini juga kekurangan air bersih, di atas kertas memompa air tanah dengan sumur dalam adalah terlarang. Kenyataanya? Pabrik-pabrik industri, gedung pencakar langit baik perkantoran, apartemen ataupun hotel memompa dengan sumur dalam, mengambil air dari kedalaman 100-200m tanpa henti. Mengapa? Karena perusahaan air minum (PAM) tidak sanggup memenuhi “dahaga” penduduknya!!!

download full paper: GTL-Perlukah Giant Seawall untuk Jakarta

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